110. Balanced Binary Tree
1、原题
Given a binary tree, determine if it is height-balanced.
For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node never differ by more than 1.
2、题意与解析
这道题目的意思很简单，就是让我们判断一个二叉树是不是一个平衡二叉树。
在这里我的思路是通过递归判断每一层的左右自树的高度。进行判断。具体看代码。
3、代码
int getHeight(TreeNode* root) {
if (root == null) {
return 0;
}
//求左右子树的高度
int l = getHeight(root->left);
int r = getHeight(root->right);
//当其子树中存在不平衡的部分或左右子树不平衡
if (abs(l - r) > 1 || l == -2 || r == -2) {
return -2;
}
return max(l,r) + 1;
}
bool isBalanced(TreeNode* root) {
if (root == null) {
return true;
}
return getHeight(root) != -2;
}
